The present invention relates to a pressure regulation apparatus ideally suited for controlling transportation of materials in either of at least two directions. The present invention further relates to a bi-directional mode carrier transportation system suitable for use in a pneumatic tube system.
In transporting of items through a pneumatic tube system, it is desirable to bi-directionally drive the system. The medium in the system therefore moves the item to a remote location while it is directed in one flow direction, and then returns the item to an origin location when the direction of medium flow is reversed. Various valve mechanisms for providing bi-directional fluid flow have been developed. For example, U.S Pat. No. 3,039,491 discloses a valve mechanism which includes two valve members The position of the first of the valve members is controlled by a solenoid. The solenoid regulates the positions of pilot valve members which in turn open or close bleed passages to position the first valve member.
A fluid-switching valve is disclosed in U.S. Pat. No. 3,722,525 as automatically reversing its position in response to flow conditions to selectively distribute pressure to selected outputs. According to U.S. Pat. No. 3,722,575, back pressure in the system will cause a diaphragm to shift and alternately open two valve disks.